A Butterfly in Tokyo
by Skeptikitten
Summary: Life is a complex system in which small changes can have catastrophic effects. When a single letter changes everything, Light Yagami becomes a pivot point in the system. What future will emerge from the chaos, and can Light and L stop it from crumbling?
1. Prologue: The Butterfly Effect

_Author's Note:_

_This will be my first fiction published in this sort of medium, so it will be interesting to see how this goes over. This idea won't leave me alone, and is fueled completely by my irritation with horrible pop culture usage of the Chaos Theory phenomenon "The Butterfly Effect". In essence, every movie or fictional work I have ever read gets this concept entirely backwards, save perhaps the 2000 film "Frequency" and, freakishly enough, the second "Back to the Future" installment. 2004's "The Butterfly Effect" was actually one of the worst._

_But I digress in my rantings, darlings. This piece will be a rather long work based on the actual rudiments of chaos theory with a little supernatural intervention thrown in due to the fandom at hand. Possible warnings for this fiction in the future include violence, sexual situations, homosexuality, language, murder, mayhem, and the mention of math. "The Butterfly Effect" was first posited by MIT meteorologist Edward Lorenz in 1972 to explain the proportional response of a minute change in start point of a function or of a small perturbation in a complex system (like the weather). _

**Prologue: The Butterfly Effect **

Life is a complex system. Its myriad interconnected parts display behavior that, taken as a whole, is not predictable from the behavior of each individual piece. Though this system is so large that its variations seem infinite and random, a structure exists within those variations. Multiple interactions between its pieces evolve the system constantly, unfolding over time to a seemingly incomprehensible pattern.

This system is highly sensitive to small disruptions, leaving multiple pathways for life to evolve. However, complex systems also have memory and past states of evolution often have an effect on present ones, particularly where humans are involved. This adaptivity to changing conditions might lead an observer of the system to conclude that its future is linear. Planned. Predictable.

In truth, life is nonlinear and a single perturbation may cause a proportional response throughout the system as a whole, drastically changing its shape forever.

If a butterfly flaps its wings in Tokyo, will it cause a tornado in England?

Light Yagami is about to become the pivot in the evolution of the system. And the butterfly? A single letter on a television screen.


	2. Chapter One: Cascade

_Author's Note:_

_Warnings for this chapter include language and violence. "Cascade" refers to the biology term "cascading failure", wherein a small change in a biological system leads to systemic failures as happens in stroke victims. _

**Chapter One: Cascade**

_December 2003_

The typographical error occurred for a simple enough reason. Sakura TV translator Keiji Nakamura had gotten only three hours of sleep the previous night, as his month-old infant was suffering from extreme bouts of colic. Despite downing what he felt was his own weight in coffee, Nakamura found the English characters swimming in front of his eyes as he translated the newest story from Los Angeles; a dozen of the most notorious criminals in America were being transferred to a new, state of the art, maximum security facility in Death Valley. He was slightly uneasy about reporting the names and faces of these criminals considering this "Kira" that was at work, but his supervisor was adamant. The boss liked the sensationalism of this vigilante, so major arrests and criminal interest stories would continue as usual.

_Well_, Nakamura mused to himself, _at least until the NPA shuts us down_. A quick glance at the clock told him that he only had five minutes to finish his work before it had to be down in editing for the evening's run.

"Shit".

No time to proof-read then. No matter- Nakamura was extremely conscientious and had never had an error found in one of his translations before.

The story aired on the evening news on Sakura TV, broadcasting to the Kanto region of Japan. Due to the heinous nature of the crimes committed by the American prisoners, Kira quickly consigned them to death with a quick flick of his pen.

Thus began the cascade. Unbeknownst to Kira, a single character in the name of one of the criminals was mistranslated from English to hiragana. As a result, the prisoner did not die as planned. Kira, of course, did not notice. The would-be god wrote far too many names now to check on the deaths of all his victims, so the survival of a single man changed little. Since the others being transferred with him died within the environs of their new facility, the murderer's continued existence made barely a ripple in the fabric of the original pattern of the universe. The two guards assigned to transport him to his new cell arrived at home on time that night, rather than the hour delay that would have occurred with their charge's death. Minute changes in the schedules of their families began- their children went a little earlier to bed, thus getting up a little earlier in the morning. They arrived at school early the next day, changing the routine of several of their teachers and friends by a few minutes.

The ripple moved outward steadily, tiny changes in the interactions of average men and women impacting each other. As a result, in May of 2004 a Japanese businessman in Los Angeles was able to catch an earlier return flight back to Tokyo, bringing the ripple with him.

The cascade had returned to its origin.


	3. Chapter Two: Dissonance

_Author's Note:_

_I do not own Death Note or any of its characters, nor do I profit from this work. Sadly._

_First, many thanks to those of you who reviewed! I have been unsure of posting in an online medium, but you have been very encouraging. I will do my utmost to keep you entertained._

_Second, the rest of the story as a whole will carry spoilers for the entire anime, despite being AU. Future chapters will have mention of L's true name. Also, beware crude language and violence, and Light's first appearance. Happy early birthday, Light-kun! _

"_Dissonance" refers to two mathematical functions that are the same except for start point, causing identical shapes shifted out of sync._

**Chapter Two: Dissonance**

_July, 2004_

Kazuhiko Kazue was furious as he wove his Honda dangerously through the late morning traffic. He wasn't even supposed to _be_ working today, much less running errands for his pig of a boss. Kazue should have been at the zoo with his daughter, as he had promised her weeks ago. That was before that loser Nakamura got his whole department sick. The man had caught some super-flu from his brother-in-law, a salaryman recently returned to the country after an extended business trip to LA.  
The bug had infected, then _reinfected_, the whole translation department, leaving the head editor's personal assistant the only one not puking up his spleen who could still translate properly from English. Since Kira tended to kill more American criminals than those of any other nationality, that meant a shit load of translation work. Demegawa, being the _devil_, had then appropriated Kazue to do his grunt work for him while his PA was indisposed. He was a cameraman, damn it all, not a gopher.

Narrowly avoiding a group of schoolgirls crossing the street, Kazue cut off at least two other drivers while changing lanes. If he didn't get to that bakery before 10 to get Demegawa's favorite pastries, the fat man would have his ass. Why it had to be a bakery clear across the city was beyond him, but Demegawa had insisted that their strawberry tarts were the best outside of Europe. Whatever. Kazue hated European and American breakfasts; miso soup and rice had been fine for his countrymen for over a hundred years, why change now? And with _sugar_, he thought disgustedly as he swerved around a taxi and an obnoxiously colored tour bus. White people had no taste, Kazue mused as he pulled a cigarette from the pack in his passenger seat. He'd make sure to keep his daughter from being influenced by American culture, that was for damn sure.

As the disgruntled cameraman struggled to light his cigarette while maintaining his breakneck speed, a taxi pulled away from the curb in front of him. Had he not been so focused on his lighter and inner rantings, Kazue might have noticed in time to avoid collision. As it was, he slammed into the front driver's side of the cab just as it angled into traffic, spinning the taxi around so its rear end impacted the cars behind. Kazue's Honda also spun, the momentum from his speed carrying him over 10 meters into the crosswalk amidst a horrible screech of wrenching metal.

The elderly man in the crosswalk, arms full of what appeared to be bakery boxes, never stood a chance.

* * *

Light Yagami was contemplating murder. Not in the abstract, philosophical sense, but the true physical meaning of the word. Visions of wrapping his hands around the scrawny white throat of his tormentor and squeezing until those huge doll's eyes went blank floated through his mind in a haze of red. It would be so satisfying. Light could almost feel the endorphins rushing through his bloodstream at the mere thought of the look on that stoic face, the surprise and alarm sure to be present there as that clever mouth was silenced. The corners of his own mouth twitched upwards slightly.

"Light-kun's smile just now is more than somewhat creepy. I wonder, is he plotting my demise? Up three percent."

And _that_ was the source of Light's sudden desire for homicide. L. Ryuzaki. Hideki Ryuga. _Whoever._ The eccentric detective had handcuffed Light to his side two weeks ago, and despite agreeing to these conditions the teenager was honestly unsure how much more he could stand. Of course, the fading bruises on his jaw from their altercation a week ago could be coloring his thoughts. Or perhaps it was the complete and total lack of privacy. Light had not been fully aware that when agreeing to be with Ryuzaki "24 hours a day", the man had meant every single minute. Even in the shower, or when Light had to use the bathroom, or when he was trying to sleep. "Trying" being the operative word, as Ryuzaki never slept for more than an hour or two at night, and Light had been thus far unable to actually catch him at it. The rest of the time, the man crouched on the bed staring at his laptop while Light tried in vain to obtain his usual eight hours. More than once he had awoken to Ryuzaki _staring_ at him, though when questioned the irritating jerk simply replied _Light-kun is surprisingly adorable when he's sleeping. I would never have guessed he was a drooler._

"I defy anyone to be around you twenty-four seven and not be somewhat homicidal. Therefore, your equating my desire to maim you with my being Kira is illogical".

Matsuda snickered from the corner of the room, Ryuzaki shooting him a disapproving glare that only increased when he realized Aizawa and Mogi were trying to hold in laughter as well. Light went back to his research, ignoring the disgruntled sound that Ryuzaki made as he blew his bangs out of his face and returned to his own screen. Apparently, he was not genius enough to catch the "leave me alone" vibe Light was sending out, however, as only a minute passed before he felt the need to reply.

"Light-kun is very mean. After all, he agreed to these particular conditions. Not to mention that Light-kun's narcissism makes him a difficult housemate as well".

Light spun in his chair, the chain of the cuffs yanking Ryuzaki forward as he stood up indignantly.

"I am _not_ a narcissist!"

More snickers erupted from Matsuda's corner, as well as outright guffaws from Aizawa and Mogi and even a slight cough-laugh from Soichiro. His own father. Traitor.

"Light-kun spends a ridiculous amount of time on his preparations in the morning, or would if I would allow it. He is constantly checking his reflection in any handy object, and frets over his wardrobe despite the fact that he will not even be leaving the building. He is obsessive about his eating and shower habits, and from public observation is overly sure of his abilities to use his looks to sway the outcome of any social situation. Either Light-kun is a narcissist, or he is gay. Probability of Light-kun being _both_ is 15 percent".

"I am NOT gay!" Light fumed, pulling the chain in his hand to drag Ryuzaki close enough so that he could grab the collar of his shirt. "And just because I am careful about my appearance does not make me a narcissist!"

Infuriatingly, Ryuzaki ignored the fist in his shirt and patted Light condescendingly on the head.

"Of course it doesn't Light-kun" Ryuzaki drawled. He unwound Light's fingers from his collar and crouched in his chair once more, reaching for the bowl of chocolate mints in front of him. "Don't worry, I am still Light-kun's friend even though he is a homosexual narcissist".

"Why thank you, Ryuzaki" Light replied sweetly. His gritted teeth somewhat ruined the honeyed effect of his voice. "You should know that I am still your friend too, even though you are a slovenly voyeuristic pervert".

Ryuzaki merely chuckled in response, the influx of sugar apparently keeping him from starting the physical fight Light was clearly trying to instigate. "Touché, Light-kun, touché".

Light settled himself back into his seat with a vaguely disappointed feeling. He had perhaps been a bit too transparent in trying to start another fight with Ryuzaki. Light was unsure of the reason, but their previous scuffle had been immensely satisfying. He didn't know whether it was because he truly wanted to hurt Ryuzaki, or whether it was simply good to have an outlet for the stress imposed upon him by his imprisonment and surveillance. A more traitorous voice in his head suggested that he may have enjoyed the fight because Ryuzaki was the first person he'd ever met who could truly challenge him. Light was, after all, terminally bored. Always the top of his class without trying. Always able to read his peers like a book. Always able to get the girl, win the match, steal the show. Bored, bored, bored. But then came Ryuzaki, and despite it being at the business end of a murder charge, Light was suddenly _not_ bored. When he wasn't being kicked in the face, stared at creepily, or accused of murder, he and Ryuzaki were able to talk about subjects his former classmates could never have understood; philosophy, mathematics, forensics, law. They played chess and Go at two in the morning. They played tennis every day at lunch (the only time the blasted cuffs came off). They alternated wins evenly between them, and Light was struck by the bizarre notion that this was what a friendship was truly supposed to be like.

They were not friends. Light knew that academically. Ryuzaki's claim that Light was his "first ever friend" was a tool in the investigation, nothing more. Living with Ryuzaki wasn't all sweetness and light either, he mused. The detective was rude, socially inept, sloppy, unhealthy, and overly informal. He stared constantly, had a host of irritating physical tics and compulsions, was a complete egomaniac, and unbelievably obstinate. Not to mention that friends do not, in general, accuse each other of serial murder. Light had to be on guard constantly for fear that something he said would up his "Kira percentage", though the teen was more than aware that number was pure bullshit. Ryuzaki pulled his percentages out of his ass, trusting his reputation to make them seem believable and cow his suspects.

Light was not cowed. For all his rantings on Kira's methods and "evil" nature, Light couldn't help thinking that Ryuzaki himself was a little like Kira. Not on that scale, of course, but L's methodology was shady at best and illegal at the worst. Even if he or Misa had confessed during their horrific confinement, any court of law would toss the evidence as not lawfully gained. The great L didn't have to stoop to investigating within the law or bother with the courts, though. His word alone was enough for every world government on the planet and Interpol. It made Light wonder, when he laid awake at night listening to the rhythmic sound of Ryuzaki's typing, why he didn't just turn them in if he was so damn sure they were Kira and Second Kira. He wasn't complaining, mind you, as he was in fact innocent.

Yes, Light was torn between wanting to kill Ryuzaki with his bare hands and wanting to draw him closer. Light had also never had a true friend, one who understood; genius was not enviable. It was cold and lonely and alienating. It didn't matter that Light had a wonderful family, good standing, high social status, athleticism, and good looks. No one could see through his elaborately constructed masks, nor cared to. Ryuzaki, at least, had Watari. Light was not so foolish as to dismiss the old man as some sort of butler as the others were wont to do. Watari was clearly on an intelligence level near L's. The technology that the Task Force used every day, the incredible building they lived and worked in, Light had deduced that they were all designed by Watari. Having thoroughly researched L's career, Light also knew that Ryuzaki had been operating as L for nearly thirteen years. The man must have been a preteen when he started, if Light was any judge of age. That implied Watari was not simply an assistant, but was in actuality L's backer. If his intuition was correct, that meant that the older man had believed enough in the potential and intellect of a child to allow him to function in a dangerous, adult profession. And L had become the best in the world. What would it be like, Light asked himself, to have that kind of understanding and support? Soichiro Yagami was proud of his son, that much was true. But the chief was always trying to shield Light, despite his having solved several "unsolvable" cases for the NPA. His reactions to his son's deductions so far in the Kira case had been shock and outright disbelief. Being relatively ordinary himself, Soichiro could not truly fathom the extraordinary in his offspring...

All right, so maybe he was a bit of a narcissist. Not to mention whinging on in his head about how tough he had it in life. Gods, the sleep deprivation was making him think like a typical teenager. Perhaps he could be a _touch_ more civil.

"Ryuzaki..."

The detective turned questioning eyes on Light, who was just opening his mouth to continue when Ryuzaki's cell phone rang. Light was thrown immediately back into a state of irritation. Strike civil, that bastard was going down. And he'd make him _eat_ that gay comment.

"Considering you make everyone _else_ turn off all electronic devices in here, that is unbelievably obnoxious".

"My house, my rules, Light-kun" Ryuzaki quipped, flipping the phone open and dangling it by index finger and thumb in front of his ear.

"Yes?"

Ryuzaki's face tightened at the voice on the line, becoming an impenetrable mask. Only Light noticed the slight air of panic in those large gray eyes.

"I see. Thank you. I'll be there right away", Ryuzaki hung up the phone, closing his eyes and taking a few deep breaths.

"It's Watari".


End file.
